1. Field of the Invention
The present invention relates to a biopsy device, and more specifically to a semi-automatic biopsy device in which the user may confirm the position of the stylet tip near the target tissue area and existence of target tissue in the stylet notch before the user fires the cannula to resect the target tissue. The present invention also relates to a biopsy device which can be adjusted to take tissue samples of varying sizes, and which has a locking mechanism to avoid inadvertent resection of tissue.
2. Discussion of the Related Art
A biopsy device is a surgical instrument which allows a medical doctor to obtain a tissue sample from a patient for diagnostic purposes, and which has particular application to removing internal tissue samples from the patient's body.
Biopsy devices typically fall into three categories: manual; automatic; and semi-automatic. Automatic biopsy devices typically include a hollow cannula through which a stylet extends. The stylet includes a tip at its distal end for insertion into a patient and a notch, adjacent the tip, in which tissue prolapses. The stylet and cannula are attached to hubs which interface with compression springs. In operation, the user first "cocks" the device external to the patient to compress the springs and prepares the biopsy device for firing. "Firing" the biopsy device refers to rapid movement of the stylet or the cannula at speeds designed to minimize patient tissue trauma. Once the user cocks the device, the user inserts the device into the patient to place the stylet tip near the target tissue area. The user fires the stylet to penetrate the target tissue area and collect tissue in the notch. Upon completion of the stylet's firing, the device automatically fires the cannula, thereby closing the notch to resect the prolapsed tissue.
A disadvantage of such prior art automatic biopsy devices is that when the user positions the stylet tip near the target tissue area, the user cannot confirm collection of target tissue into the stylet notch prior to automatic firing of the cannula. A semi-automatic biopsy device allows a user to confirm prolapse of target tissue in the stylet notch. With a semi-automatic device, the user manually advances the stylet into the target tissue area. The user then may confirm correct positioning and prolapse of tissue in the notch by appropriate imaging methods before resection of the target tissue by firing the cannula.
Stylets of conventional semi-automatic devices typically resect a fixed, invariable tissue sample size. Due to the varied applications for biopsy devices in different parts of the anatomy (e.g., liver, lungs, throat, breast, etc.), the user often must take tissue biopsies of varied size. Therefore, a conventional biopsy device may not be suitable for all diagnostic applications.
In addition, conventional semi-automatic devices often utilize the same trigger mechanism to fire both the stylet and the cannula. The user typically presses the trigger mechanism to fire the stylet and to fire the cannula. With such a device, the user does not have an opportunity to confirm correct positioning of the stylet.